Adaptable communication sensitivity for an implantable medical device

Technical field

This application relates generally to implantable medical devices and, more specifically but not exclusively, to adapting a threshold that is used to determine whether an external device is transmitting to an implanted device.

Background

Implantable medical devices may be employed in various applications. For example, an implantable cardiac device may perform one or more functions including sensing signals generated in a patient's heart, pacing the heart to maintain regular contractions, and providing defibrillation shocks to the heart. Similarly, an implantable stimulation device may be used to apply stimulation signals to a patients muscular tissue, neurological system, or some other area of the patient's body.

In practice, there may be a need to communicate with an implantable medical device after it has been implanted in a patient. For example, an external monitoring device located in a person's home, a doctor's office, a clinic, or some other suitable location may be used to retrieve information collected by and/or stored in the implanted medical device. In the case of an implanted cardiac device, such information may include sensed cardiac activity data that a treating physician may analyze to learn about the patient's health. Similarly, an external programming device located in any of the above locations may be used by a treating physician to change the operating parameters of the implanted medical device. Such parameters may include, for example, the timing or magnitude of stimulation pulses generated by the implanted medical device.

In a typical implementation, an implanted medical device utilizes radio frequency ("RF") telemetry to communicate with an external device. Consequently, the implanted medical device may include an RF transceiver that is adapted to transmit and receive RF signals. In such an implementation, however, it is generally desirable to leave the transceiver in a powered-off or low power state as much as possible since the transceiver may consume a relatively large amount of power. Here, it should be appreciated that the replacement of the battery in an implanted medical device involves a surgical procedure. Hence, long battery life is an important aspect of such a device.

Some types of implanted medical devices employ a wakeup scheme whereby an implanted device will periodically turn on its transceiver (e.g., its receiver) to determine whether an external device is attempting to establish a communication session. For example, whenever an external device wishes to establish communication with an implanted medical device, the external device may periodically transmit polling messages (e.g., connection requests) over one or more designated RF channels. Each of these polling messages may include information relating to establishing the communication such as, for example, an identifier that uniquely identifies the implanted medical device.

Every time the transceiver of the implanted medical device is turned on (e.g., at defined intervals), the transceiver may conduct an RF scan to determine whether the external device is transmitting polling messages. This may involve, for example, performing an ID scan that checks each RF channel for any messages that include an identifier associated with that particular implanted medical device. In the event such a message is detected, the implanted medical device transmits one or more signals (e.g., in accordance with a handshake protocol) to establish communication with the external device.

In practice, a transceiver of an implanted medical device may consume a relatively significant amount of power even when a conventional wakeup scheme is used. For example, it may be desirable for an implanted medical device to be able to respond to polling messages within a relatively short period of time, for example, so that a treating physician need not wait several minutes to establish communication with the implanted medical device. The implanted medical device may therefore perform its scans at relatively frequent intervals to achieve a quick response time. Such frequent scanning may, however, increase the amount of power consumed by the implanted medical device.

In some cases, a wakeup scheme may involve staged detection to reduce the amount of power consumed by the implanted medical device. For example, such a scheme may employ a simple detection stage that samples RF energy and a more robust scanning stage that analyzes any detected signals to determine whether these signals are from an external device that is attempting to establish communication with the implanted medical device. Here, the simple detection stage may repeatedly perform an energy "sniff" in the RF channel or channels of interest. By starting a detection search with this low-level and relatively coarse energy assessment stage, the implanted medical device may avoid using the relatively high power robust scanning stage during those times when the external device is not transmitting a signal which, in practice, is usually the case for most of the lifetime of the implanted medical device. Hence, additional power savings may be achieved with this type of wakeup scheme in comparison to a wakeup scheme that does not employ staged detection.

Summary

A summary of several sample aspects of the disclosure and embodiments of an apparatus constructed or a method practiced according to the teaching herein follows. It should be appreciated that this summary is provided for the convenience of the reader and does not wholly define the breadth of the disclosure. For convenience, one or more aspects or embodiments of the disclosure may be referred to herein simply as "some aspects" or "some embodiments."

The disclosure relates in some aspects to adaptation of a wireless communication threshold for an implantable medical device. Such a threshold may be used, for example, to determine whether an external wireless device is attempting to establish communication with an implanted device. In some aspects, the implanted device may use the threshold to determine when to move from one communication mode to another communication mode. For example, during a low power energy sensing (e.g., sniffing) mode a receiver of the implanted device may be enabled intermittently. Any signal energy detected during the sniffing mode may be compared with the threshold to determine whether to transition to a more robust communication mode (e.g., which may be less power efficient). During the more robust mode, the receiver may be enabled for longer periods of time to receive more signal information and/or the received signals may be processed more extensively in an attempt to recover information conveyed by the signals.

In some aspects, the threshold may be adapted in an attempt to determine an optimum threshold level in view of current conditions at the implanted device. For example, the threshold level may be automatically adapted to account for current environmental conditions, implant conditions, device conditions, or other conditions that may affect reception of wireless signals at an implanted device.

In some aspects, the determination of an optimum value for the threshold involves a tradeoff relating to the detection sensitivity of the receiver. For example, the use of a higher sensitivity may enable more effective detection of a target signal from the external device. However, a high sensitivity also may result in detection of signals that are not desired (e.g., noise or interfering signals from some other device). The detection of these undesirable signals may, in turn, result in false wakeups where the implanted device unnecessarily transitions to the higher power mode to acquire and process signals that are not target signals. In view of the above, the adaptation process may be configured to set the threshold to a lower value when the implanted device is operating in a low noise environment and to a higher value when the device is operating in a noisier environment.

The disclosure relates in some aspects to adaptation of a threshold based on at least one maximum energy level derived from one or more sets of energy sample data (e.g., representative of intrinsic noise and/or environmental noise). For example, an implanted device may acquire a defined number of samples and select a threshold value based on a maximum energy level associated with the samples. In this way, the threshold may be set to a value that is slightly higher than a noise and/or interference floor associated with the sample data. In some aspects, the maximum energy level may be selected from a plurality of maximum values associated with different data sets. In some aspects, a data set may comprise histogram information. For example, the maximum energy level may be derived from a tail (e.g., a first tail) of a set of histogram data.

The disclosure relates in some aspects to adaptation of a threshold based on the number of false wakeups that occur during a period of time. For example, upon detection of a given number of false wakeups, an implanted device may increase a threshold, temporarily cease sniffing operations, disable wakeup detection, or perform some other suitable operation.

Brief description of the drawings

These and other features, aspects, and advantages will be more fully understood when considered with respect to the following detailed description, the appended claims, and the accompanying drawings, wherein:

FIG. 1 is a simplified diagram of a communication system including an implantable medical device and an external device;

FIG. 2 is a flowchart of an embodiment of operations that may be performed to establish communication between an implantable medical device and an external device;

FIG. 3 is a simplified block diagram of an embodiment of communication-related components of an external device;

FIG. 4 is a flowchart of an embodiment of operations that may be performed to adapt a threshold;

FIG. 5 is a flowchart of an embodiment of a threshold adaptation algorithm;

FIG. 6 is a simplified diagram illustrating an embodiment of data set acquisition;

FIG. 7 is a flowchart of an embodiment of a threshold adaptation algorithm;

FIG. 8 is a flowchart of an embodiment of a threshold adaptation algorithm;

FIG. 9 is a simplified diagram illustrating an embodiment of a histogram;

FIG. 10 is a simplified diagram of an embodiment of an implantable stimulation device in electrical communication with one or more leads implanted in a patient's heart for sensing conditions in the patient, delivering therapy to the patient, or providing some combination thereof; and

FIG. 11 is a simplified functional block diagram of an embodiment of an implantable cardiac device, illustrating basic elements that may be configured to sense conditions in the patient, deliver therapy to the patient, or provide some combination thereof.

In accordance with common practice the various features illustrated in the drawings may not be drawn to scale. Accordingly, the dimensions of the various features may be arbitrarily expanded or reduced for clarity. In addition, some of the drawings may be simplified for clarity. Thus, the drawings may not depict all of the components of a given apparatus or method. Finally, like reference numerals may be used to denote like features throughout the specification and figures.

Detailed description

The description that follows sets forth one or more illustrative embodiments. It will be apparent that the teachings herein may be embodied in a wide variety of forms, some of which may appear to be quite different from those of the disclosed embodiments. Consequently, the specific structural and functional details disclosed herein are merely representative and do not limit the scope of the disclosure. For example, based on the teachings herein one skilled in the art should appreciate that the various structural and functional details disclosed herein may be incorporated in an embodiment independently of any other structural or functional details. Thus, an apparatus may be implemented or a method practiced using any number of the structural or functional details set forth in any disclosed embodiment(s). Also, an apparatus may be implemented or a method practiced using other structural or functional details in addition to or other than the structural or functional details set forth in any disclosed embodiment(s).

FIG. 1 illustrates a simplified diagram of a communication system 100 including an implantable medical device 102 that is implanted within a patient P and a device 104 that is located external to the patient P. The implanted device 102 and the external device 104 may communicate with one another via a wireless communication link 106 (as represented by the illustrated symbol).

In this example, the implanted device 102 is an implantable cardiac device including one or more leads 108 that are routed to the heart H of the patient P. For example, the implanted device 102 may be a pacemaker, an implantable cardioverter defibrillator, or some other similar device. It should be appreciated, however, that the implanted device 102 may take other forms. For example, in some embodiments the implanted device 102 may be a neuro-stimulation device or some other type of implantable device.

The external device 104 also may take various forms. For example, the external device 104 may be a base station, a programmer, a home safety monitor, a personal monitor, a follow-up monitor, a wearable monitor, or some other type of device that is configured to communicate with an implanted device.

In a typical embodiment, the communication link 106 is an RF link. In some embodiments the communication link 106 may operate within the medical implant communication service ("MICS") band. It should be appreciated, however, that the teachings herein may be employed in conjunction with other RF bands such as a band in the 2.45 GHz range or some other band. In other embodiments the communication link 106 may take other forms including, for example, an inductive telemetry link.

The communication link 106 may be used to transfer information between the devices 102 and 104 in conjunction with various applications such as surgical procedures, clinical visits, data acquisition, remote follow-up, remote home-monitoring, and portable or wearable patient monitoring/control systems. For example, when information needs to be transferred between the devices 102 and 104, the patient P moves into a position that is relatively close to the external device 104, or vice versa. As will be discussed in more detail below, the external device 104 may then be configured to transmit periodic signals to the implanted device 102 to initiate communication between the devices 102 and 104.

The implanted device 102 may employ a wakeup scheme to reduce power consumption associated with determining whether the external device 104 is attempting to establish communication with the implanted device 102. For example, a transceiver component (e.g., a receiver) of the implanted device 102 that is used for communicating with the external device 104 may normally be turned off or set to a low power mode in some other manner. This component may then be turned on from time to time to sense for signals from the external device 104. In some embodiments the wakeup scheme employs staged detection whereby the result of a low-level scan (e.g., an RF energy sniff) during a low power operational mode is used to determine whether to transition to another operational mode to conduct a high-level scan (e.g., a full scan of one or more communication channels).

The detection scheme may be adaptive whereby one or more parameters are adjusted to increase the likelihood of detection of a target signal from the external device 104 and to reduce any adverse consequences (e.g., increased power consumption) that result from detection of non-target signals. For example, a threshold used during the low-level scan may be adapted to reduce the number of false wakeups that occur at the implanted device 102.

In some aspects, a threshold may be defined by acquiring discrete samples of environmental and/or intrinsic noise (e.g., over a defined period of time), determining energy level values of those samples, taking a statistical measure of the energy sample values, and adding a defined increment to the statistical measure to provide a threshold value. In some aspects, the statistical measure may be based on a maximum sample value derived from the samples. In some aspects, the statistical measure may be based on zero value and non-zero value sample sequences (e.g., of a histogram) associated with the defined number of samples.

These and other detection techniques will now be described in more detail in conjunction with FIGS. 2, 3, and 4. FIG. 2 illustrates several sample operations that may be performed by an implanted device to establish communication with an external device. FIG. 3 illustrates several sample components of an embodiment of a device 300 (e.g., communication components of the implanted device 102). FIG. 4 illustrates several sample operations that may be performed by an implanted device to adapt a threshold.

For convenience, the operations of FIG. 2 (or any other operations discussed or taught herein) may be described as being performed by specific components (e.g., components of the device 300). It should be appreciated, however, that these operations may be performed by other types of components and may be performed using a different number of components. It also should be appreciated that one or more of the operations described herein may not be employed in a given implementation.

Referring initially to FIG. 2, the implanted device 102 may wake up on a repeated basis to determine whether the external device 104 is transmitting signals in an attempt to establish a communication session. As represented by block 202, the implanted device 102 may thus commence a low power mode RF sniffing operation at designated times. Referring to the example of FIG. 3, a receiver component 302 in a transceiver 304 may be intermittently activated (e.g., powered on according to a defined scan interval) to scan for signals within a given RF frequency band.

In some embodiments, at a given point in time the devices 102 and 104 may communicate via any one of several channels that are defined for a given frequency band. In these cases, the devices 102 and 104 may elect to use a channel that provides the most effective communication medium (e.g., that has the least amount of interference) at a given point in time. In some embodiments the devices 102 and 104 may communicate via any of the channels defined for the MICS band. When the external device 104 initially attempts to establish a communication session with the implanted device 102, the external device 104 selects a particular channel on which to transmit its request messages. Consequently, during the low power sniff operation, the receiver 302 may be configured to scan each of the channels of the designated communication band (e.g., separately or in one or more groups) to determine whether the external device 104 is currently sending messages over any of the channels.

As represented by block 204, the receiver 302 thus attempts to detect signal energy within a certain frequency range for a defined period of time. The signal detection of block 204 may advantageously be a relatively low power operation. Here, rather than scanning for a long period of time in an attempt to acquire an entire message transmitted by the external device 104, the receiver 302 may sense for a short period of time (e.g., a few milliseconds) and utilize a low power signal detector 306 (e.g., an energy detector) to detect a signal. For example, the signal detector 306 may be configured to simply detect the magnitude of a signal, an energy level of a signal, or some other suitable attribute of a received signal. Hence, the operation of block 204 may involve partially "waking up" the device 300 since, for example, full operation of its communication components may not be needed at this point. In some embodiments such a low power, partially awakened mode may be invoked by enabling (e.g., powering on) only a portion of the communication components of the device 300 (e.g., component 302 or component 304). Also, the low power, partially awakened mode may be invoked by modulating the duration for which one or more communication components are enabled (e.g., powered on). For example, the partially awakened mode may involve repeatedly enabling, over the course of a scan interval, one or more communication components for a relatively short period of time. In this case, power savings may thus be achieved by not turning on the component or components for the entire interval.

As represented by block 206 of FIG. 2, the signal detector 306 may compare the detected signal, if any, with a threshold 308. For example, in some embodiments a received signal strength indication ("RSSI") associated with the detected signal may be compared with the threshold 308. Such a comparison may thus serve as a basis for determining whether to perform a more robust (e.g., comprehensive) scan.

In the event the designated signal property (e.g., RSSI) detected at block 204 is less than the threshold 308 at block 206, an assumption may be made that the external device 104 is not transmitting a target signal to the implanted device 102. In this case, the operational flow may return to block 202 to wait for the next RF sniff interval (e.g., by operation of a receive mode controller 310).

In the event the signal property (e.g., RSSI) detected at block 204 equals or exceeds the threshold 308 at block 206, an assumption may be made that the signal is from the external device 104. Consequently, as represented by block 208 the device 300 (e.g., by operation of the receive mode controller 310) may wakeup from the low power mode to perform a more comprehensive scan on one or more designated channels for signals from the external device 104. In some embodiments, the channel or channels scanned at block 208 may be the same as those scanned at block 204. Here, the receiver 302 may be adapted to scan each channel for a sufficiently long period of time to acquire any messages transmitted by the device 104.

To accomplish such a comprehensive scan, the operation of block 208 may thus involve "waking-up" one or more additional components of the device 300. For example, the higher-power, fully awakened mode may be invoked by enabling (e.g., powering on) all or substantially all of the communication components of the device 300. In addition, in contrast with certain embodiments of the partially awakened mode, the fully awakened mode may involve continually enabling one or more communication components over the course of an entire scan interval. Thus, the comprehensive scan of block 208 may be longer in duration and/or may consume more power than the sensing operations of block 204.

As represented by block 210, the receiver 302 and/or a communication processor 314 may be adapted to analyze a received signal to determine whether it is a target signal from the external device 104. To this end, the receiver 302 may be configured to extract any messages that are encoded in the signals. The communication processor 314 may then determine whether the message includes an identifier that identifies the implanted device 102.

As discussed in more detail below, the receiver 302 also may maintain a record of the signal property (e.g., RSSI level) that resulted in detection of a target signal. In some aspects, this type of information may be used, for example, to set the level of the threshold 308. In the example of FIG. 3, this information is designated as econnect 312 (e.g., the energy associated with a successful connection).

As represented by block 212, in the event a message destined for the implanted device 102 is detected, the implanted device 102 may commence communication with the external device 104. For example, the communication processor 314 may proceed to establish a connection with the external device 104 by generating an appropriate response message and sending the message to the external device 104 via a transmitter 316.

As represented by block 214, in the event a target signal is not detected at block 210, a false wakeup condition may be indicated. For example, the presence of noise or in-band communication by other devices may result in a successful comparison at block 206 and, consequently, an unwanted transition to a high-level scan at block 208. As will be discussed in more detail below, the implanted device 102 may thus comprise a false wakeup detector 318 that maintains a false wakeup count 320. If the false wakeup detector 318 detects a given number of false wakeups (e.g., as defined by a false wakeup threshold) within a defined period of time, the threshold 308 may be adapted and/or some other course of action may be taken to reduce the number of occurrences of such unwanted high-level scans. For example, the threshold 308 may be adapted (e.g., increased) so that the receiver 302 is less sensitive to noise or other signals within the frequency band of interest. In some embodiments, the threshold 308 may not be adapted in the event the false wakeup is associated with a signal from a compatible external device (e.g., an external device made by the same manufacturer as the external device 104) since the detected energy level may correctly correspond to a target signal.

In some embodiments the false wakeup threshold may be adaptable. For example, the false wakeup threshold may be adapted based on current and/or past environmental conditions. In some implementations the false wakeup threshold is adapted based on the frequency of false wakeups. For example, if false wakeups have not been detected for a relatively long period of time (e.g., one week or one month), the false wakeup threshold may be increased.

In some embodiments, the false wakeup detector 318 may track the number of false wakeups that occur over a longer period of time and cease energy sniffing operations in the event this number exceeds a defined threshold value (e.g. 100 or 1000). For example, if this threshold value is exceeded during a defined period of time, the implanted device 102 may cease background sniffing operations and just rely on a scheduled wakeup scan (e.g., that occurs every two hours) to determine whether the external device 104 is attempting to establish communication. The scheduled wakeup scan is described in more detail below. The background sniffing operations may then be re-enabled, for example, by reprogramming the implanted device 102 (e.g. via telemetry), or when a scheduled wakeup occurs. In some aspects the threshold value may be programmable. For example, in some implementations the threshold value may be adjusted by a defined amount depending on a current operating condition (e.g., the rate that false wakeups are occurring) or some other factor. In some implementations the threshold value may be set to or adjusted up to a maximum value.

After the false wakeup-invoked operations are performed, the operational flow may return to block 202 to wait for the next RF sniff interval (e.g., by operation of the receive mode controller 310).

As mentioned above, in some aspects the threshold used for the signal detection operation may be adaptable. For example, due to one more factors such as RF interference (e.g., the background radio noise level) in the current environment, intrinsic noise of the implanted device 102, and implant site characteristics. As an example of the latter factor, the electrical characteristics of the tissue at the implant site or the electrical interface of the tissue and one or more conductive surfaces of the implanted device may affect the reception of signals at the implanted device. Thus, different thresholds may be defined for devices implanted in different patients, even under the same environmental conditions and given identical device characteristics. Similarly, even for a single device implanted in a given patient, one threshold value may be specified immediately after implant and a different threshold specified at some later point in time. As a result of the above factors, it is desirable to automatically adapt the threshold 308 (e.g., a sniff energy threshold) to limit the number of false wakeups while maintaining good sensitivity to target signals from the external device 104.

FIG. 4 illustrates several sample operations that may be performed to adapt a threshold. Again, for illustration purposes, the operations of FIG. 4 may be described in the context of the system 300 of FIG. 3 which includes a threshold adapter 322.

In some embodiments the implanted device 102 may support multiple threshold adaptation algorithms. Accordingly, as represented by block 402 of FIG. 4, a particular algorithm may be selected for the threshold adaptation operations. For example, in some embodiments the algorithm may be selected by a treating physician during implant, during a clinical follow-up, or at some other time. As discussed below, the implanted device 102 may include functionality that enables the implanted device 100 to be programmed (e.g., to use the selected algorithm).

A particular algorithm may be selected based on various factors. For example, certain algorithms may result in the implanted device 102 having higher detection sensitivity than other algorithms. Hence, a decision may be made to use a given algorithm if it is determined that the implanted device 102 may operate in a particular environment (e.g., a low noise environment) the majority of the time. Several examples of threshold adaptation algorithms are described below in conjunction with FIGS. 5-9.

In some embodiments the implanted device 102 may automatically select the algorithm. For example, the implanted device 102 may include an algorithm selector 324 that is configured to select the algorithm based on the characteristics of the current environment (e.g., current RF noise levels), prior detection performance (e.g., the number of false wakeups or missed target signals), power consumption considerations, or some other suitable operating characteristic. To this end, the implanted device 102 may include appropriate functionality to identify one or more of the above operating characteristics.

As represented by block 404 of FIG. 4, at some point in time the threshold adapter 322 may elect to adapt the threshold 308. As will be discussed in more detail in conjunction with FIGS. 5-9, in some aspects the threshold 308 may be adapted on a repeated (e.g., periodic) basis. In addition, in some cases the threshold 308 may be adapted if a defined number of false wakeups occur within a defined period of time.

In the event threshold adaptation is commenced at block 406, the receiver 302 may be configured to sense signals (e.g., sniff energy in one or more RF channels) to generate one or more sets of energy samples 326 (block 408). As will be discussed in more detail below, each sample set 326 may comprise a defined number of samples. In addition, in some implementations a sample set 326 may comprise a histogram. In some aspects, the operation of block 408 may comprise a background operation that is invoked at defined intervals (e.g., a sniff comprising 8 samples is acquired every 30 seconds).

As represented by block 410, a sample processor 328 may process the sample set(s) 326 to determine a maximum energy level associated with the sample set(s) 326. For example, as described below in conjunction with FIGS. 5-7, in some embodiments the sample processor 328 may determine a maximum energy level by identifying a maximum value from one or more sample sets 326. As described below in conjunction with FIGS. 8 and 9, in some embodiments the sample processor 328 may determine a maximum energy level by identifying a tail (e.g., the first tail) of a histogram.

As represented by block 412, the threshold adapter 322 may define (e.g., update) the threshold 308 based on the sample set(s) 326. For example, the threshold adapter 322 may set the threshold 308 to the maximum energy level from block 410 plus a suitable safety margin.

As represented by block 414, the false wakeup detector 318 may concurrently monitor for false wakeups (e.g., as described herein). In the event too many false wakeups are detected, threshold adapter 322 may further adapt the threshold 308. In addition, as will be described below, the implanted device 102 may perform other operations as a result of the detection of too many false wakeups.

FIG. 5 illustrates an embodiment of an algorithm 500 that may be employed, for example, to adapt a threshold in response to changes in environmental conditions and/or device conditions. For example, in some aspects the automatically adjusted threshold provided by the algorithm 500 may have a long wakeup range (e.g., a lower threshold) in low noise environments and a short wakeup range (e.g., a higher threshold) in noisier environments.

Briefly, the algorithm 500 may adapt the threshold every time a defined number (e.g., 500) of new background samples (e.g., noise level values) are collected in conjunction with a previous collection of the defined number of background samples. This adaptation operation may increase or decrease the threshold depending on a maximum energy level (e.g., noise level) represented by the samples. In addition, if 2 false wakeups occur within a defined period of time (e.g., two hours), the threshold may be automatically increased. In addition, once the second false wakeup is detected, sample sniffing may be disabled for the remainder of that defined period of time.

As represented by block 502, when the implantable device 102 is shipped from the manufacturer, several parameters of the implantable device 102 may be set to default settings. For example, the threshold (e.g., a sniff threshold) may be set to a default value that is defined relative to determined or estimated background noise levels and target signal levels. In some embodiments this default value may be set to a value that is slightly less than a maximum energy level detectable by the implantable device 102. As a specific example, in an implantable device 102 that utilizes a 6-bit analog digital converter ("ADC"), the default value may be set to 0x30. Similarly, maximum sample values E_N1 and E_N2 associated with different sample subsets may be set to the same default value or some other default value. Finally, the econnect parameter 312 (FIG. 3) may be set to a default value such as 0.

As represented by block 504, after implant, the implanted device 102 is configured to acquire one or more sets of energy sample information (e.g., sample set(s) 326). This operation may comprise, for example, the background RF energy sniffing operations described above at FIG. 4. To enable the implanted device 102 to quickly commence threshold update operations after implant, the implanted device 102 may be configured to acquire the initial set of sample values at a rate that is faster than the normal background sample acquisition rate (e.g., that involve one sniff every 30 seconds).

In some aspects, each acquired set may comprise a defined number (e.g., 500) of energy sample values. The following describes a scenario where the implanted device 102 acquires two subsets of sample values. It should be appreciated, however, that other implementations may utilize a different number of sample subsets.

The sample subsets may be acquired in various ways. For example, in some embodiments the implanted device 102 may acquire a sample subset, use the subset information, then acquire new subset information (e.g., discarding the prior reformation), use the new subset information, and so on. In some embodiments the implanted device 102 may acquire a sample subset through the use of a sliding sampling window. FIG. 6 illustrates an example of overlapping sliding sampling windows. Here, first and second sliding windows 602 and 604 are used to illustrate the relative timing of two overlapping sample subsets. It should be appreciated that FIG. 6 illustrates but one example of sample subsets and that sample subsets may be defined in other ways in accordance with the teachings herein.

As mentioned above at FIG. 4, the sample processor 328 may determine a maximum value associated with each sample subset 326. For example, the sample processor 328 may determine a maximum sample value E_N1 associated with a first sample subset (e.g., sliding window 602) and determine a maximum sample value E_N2 associated with a second sample subset (e.g., sliding window 604).

A maximum sample value associated with a given sliding window may be generated in various ways. For example, in some implementations the sample processor 328 may simply maintain a single value that represents the maximum value seen over a given window of data. Thus, as each new sample value is added to the set, the sample processor 328 may compare that value with the current maximum value and update the current maximum value, as necessary. In addition, when a sample that defined the current maximum value is shifted out of the current sample set, the sample processor 328 may reset the current maximum value based on the highest sample value that remains in the set.

As represented by block 506 of FIG. 5, once the defined number of samples is collected and the maximum sample values E_N1 and E_N2 are determined, the implanted device 102 may update the threshold 308 based on the maximum sample values E_N1 and E_N2. For example, the sample processor 328 may identify the maximum of E_N1 and E_N2 to define a maximum energy level and the threshold adapter 322 may set the threshold 308 to this maximum energy level plus a safety margin (e.g., 2 ADC counts).

In some embodiments the initial value for the threshold 308 may be determined based on one of the maximum sample values (e.g., E_N1). For example, upon implant or some other event that resets the contents of the subsets, after the data samples for a first one of the subsets are acquired and the maximum value determined for that subset, the operations of block 506 may simply involve setting the threshold 308 to that maximum value plus the safety margin. Then, after the data samples for the second one of the subsets are acquired and the maximum value determined for that subset, the operations of block 506 may involve selecting the maximum of the two maximum values associated with the two subsets as described above.

After the threshold 308 is updated, the implanted device 102 continues to perform its background device sniffing operations at block 504. That is, implanted device 102 may continue to acquire samples, update the subsets, and update the maximum sample values.

The implanted device 102 may therefore regularly adapt the threshold 308 at block 506 based on the signals that are currently being sensed. Consequently, in the event there is a change in environmental conditions (e.g., as discussed herein) at the implanted device 102, the threshold 308 may be increased or decreased as the sensed energy associated with these conditions increases or decreases. Thus, when the implanted device 102 is in a relatively noisy RF environment, the threshold 308 may be set to a higher value thereby decreasing the RF detection sensitivity of the implanted device 102. Conversely, when the implanted device 102 is in a relatively quiet RF environment, the threshold 308 may be set to a lower value thereby increasing the RF detection sensitivity. By adapting the threshold in this manner, the implanted device 102 may be able to effectively identify target signals in various environments.

The description continues in the full USPTO document.